Effect of Heat Treatment on the Phase Composition, Microstructure and Mechanical Properties of Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 High-Entropy Alloys

Abstract

High-entropy alloys exhibit some interesting mechanical properties including an excellent resistance against softening at elevated temperatures. This gives high-entropy alloys (HEAs) great potential as new structural materials for high-temperature applications. In a previous study of the authors, oxidation behavior of Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 high-entropy alloys at T = 800 °C, 900 °C and 1000 °C was investigated. Si-alloying was found to increase the oxidation resistance by promoting the formation of a continuous Al2O3 layer, avoiding the formation of AlN at T = 800 °C. Obvious phase changes were identified in the surface areas of both alloys after the oxidation experiments. However, the effects of heat treatment and Si-alloying on the phase transition in the bulk were not investigated yet. In this study, Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 high-entropy alloys were heat-treated at T = 800 °C and T = 1000 °C to investigate the effect of heat treatment on microstructure, phase composition and mechanical properties of both alloys. The results show that alloying Al0.6CrFeCoNi with Si caused a phase transition from dual phases consisting of BCC and FCC to a single BCC phase in an as-cast condition. Furthermore, increased hardness for as-cast and heat-treated samples compared with the Al0.6CrFeCoNi alloy was observed. In addition, the heat treatment facilitated the phase transition and the precipitation of the intermetallic phase, which resulted in the change of the mechanical properties of the alloys.

Effect of annealing heat treatment on microstructure and mechanical properties of nonequiatomic CoCrFeNiMo medium-entropy alloys prepared by hot isostatic pressing

“…Experimental results about NiCoFeCrGa showed that the cooling rate could lead to a selfsimilarity of the solidified structure formed in the specimen and confirmed the grouping of Co, Fe, and Cr in the FCC phase [13]. Moreover, two elements were added to the CoCrFeNi-based alloys to form some novel HEAs [7], such as AlCoCrFeNbNi [14], Al 0.6 CrFeCoNiSi 0.3 [15], and Al 0.5 CoCrFexNiTi 0.5 [16], whose microstructure and mechanical properties had been extensively studied.…”

Mechanical properties and water vapour corrosion behaviour of AlxCoCrFeNi high-entropy alloys

“…Moreover, research into the mechanism of the hightemperature steam corrosion of high-entropy alloys is still in the stage of describing the basic corrosion phenomenon. [19][20][21][22] The addition of Al, Cr and other elements can promote the formation of BCC phase, and can lead to the formation dense Al 2 O 3 and Cr 2 O 3 lms at high temperature to prevent further corrosion of the material. 23 J. M. Guilemany et al found that the oxidation layer was uniform and continuous at 900 °C, and speculated that 900 °C was the boundary temperature for oxidation resistance.…”

Heat Treatment Induced Structural Transformations and High-Temperature Oxidation Behavior of Al21Co22Cr22Fe13Ni22 High-Entropy Coatings Produced by Non-Vacuum Electron Beam Cladding

“…When annealing as cast Al-Cr-Co-Fe-Ni HEAs at 600-1200 • C, B2, fcc, and σ phases precipitate in solid solutions matrix, which can affect the properties of the alloy. For instance, the effect of B2-and σ-phase precipitation in an AlCrCoFeNi HEA with a low Cr content during annealing for 8 h at 600-1000 • C was described in [12] by Shen et al, the hardening of the Al0.5CoCrFeNi alloy by B2 nanoprecipitations after annealing at 650 • C for 0.5-8 h was described in [13] by D ąbrowa et al while the effect of annealing the Al0.6CrFeCoNi alloy at temperatures from 800 to 1000 • C was considered in [14]. The paper of Butler et al [15] describes the phase stability of alloys with different Al contents at 700 and 1050 • C. Zhang et al [16] used experimental and calculation methods to study in detail the phase stability and the redistribution of elements in alloys with different Al contents during long-term holding up to 1250 • C. Munitz et al [17] described the changes in the local phase composition in the dendritic and interdendritic regions of the AlCrCoFeNi alloy after annealing from 650 to 1200 • C for 3 h and evaluated the change in the strength characteristics.…”